Aran'gar specifically stated its tastes had expanded as part of accommodating the change in gender. In other words, still attracted to women, but now interested in men as well. As for Rahvin, his sexuality is so obviously tied to his self-esteem, it's pretty obvious that he'd have had obvious male partners in his stable. If anything, he'd be even more desperate to make sure the males were devoted to him than the women, given the WoT perspective on gender differences. I wonder how much Graendal really was into sex, and how much was just about shock value. She probably did it a whole lot with anything with a pulse, because she isn't one to do things by halves, but I wouldn't be surprised if that was a deliberate choice to check off every box she could think of, instead of true indulgence in repressed desires. She and Semirhage seem kind of asexual to me, insomuch as they get their rocks off with more abstract appetites.
I was trying to make the point that it would not have been hard for RJ to have easily made things happen if he had been trying to make the point about sexuality. Clearly Rhavin was not bisexual nor was Balthamel before his body swap. I was trying (unsuccessfully) to make the point that it would not have been out of place if RJ had made them both bisexual or Aginor gay etc
I tend to agree with you in how Graendal and Semirhage both came across as slightly asexual in terms of getting off on their other appetites. It is clear that Graendal at least did participate in all kinds of "pleasures" though ... but I agree that s had more to do with the perception she was deliberately trying to project. I think that is made clear just from understanding her Pre-Shadow persona. I always got the impression she was mocking the broader world for being unable to live up to her previous standards of self discipline.